The next thing to do is check the components. You want first to check the Duct fuse
. Usually mounted beside the control thermostat or on the blower housing. If that is good and the thermostat is good you would want to check the gas assembly components. The flame detector has a bi-metal inside it that powers up the ignitor. If it is open(no continuity) then the ignitor and gas coils cannot get power.
If that is good I want to check the ignitor for continuity. If open the ignitor won't glow and it won't allow the gas coils to open either. If both of those are fine I replace the gas coils, they tend to work sometimes and get hot fail then cool down and work some more, in other words checking them with a meter will not prove they are good so replace em if the heat works some but quits. (Click on pictures to enlarge)